Embodiments of the invention relate to X-ray systems, and in particular to a method and apparatus for adjusting a field of view for exposure of an x-ray system, and an X-ray system.
FIG. 1 shows a prior art digital X-ray system 100 that includes an Overhead Tube Suspensory (OTS) system 101 for moving an X-ray source, an OTS console 102, a collimator 103 constituting the X-ray source (other components constituting the X-ray source are not shown due to the angle of view), a movable examining table 104, and a positioner 105 for moving the examining table 104. The collimator 103 is typically mounted below the tube that emits X-rays, which impinges upon the patient through a shutter of the collimator 103, wherein the size of the shutter of the collimator 103 defines the irradiation range of X-rays, i.e., the size of the region of the field of view for exposure (FOV) 106. The lateral positions of the tube and the collimator determine the position of the field of view for exposure on the patient. It is well known that X-rays are harmful to humans, thus it is required that X-rays are controlled so that it impinges only upon the part to be examined, of the patient, while its irradiation range should be large enough to satisfy all of regions to be examined.
In the current digital X-ray system 100, for each X-ray examination, a radiographer is required to check whether the field of view for exposure 106 of X-ray is suitable or not. During checking, the radiographer turns on the illumination light of the collimator 103, and a collimator beam 107 will form an exposure region on the patient. The exposure region is consistent with the field of view for exposure 106 of the X-ray, so that whether the field of view for exposure 106 is suitable or not may be checked. If the field of view for exposure can not satisfy exposure requirement, the size and position of the field of view are required to be adjusted. The position of the X-ray source may be adjusted by manually moving the OTS and/or the positioner, to adjust the position of the FOV on the patient. For an advanced X-ray system, it is often equipped with an automatic positioning function, which can help the radiographer in controlling the OTS so as to automatically move into the preset position. However, existing digital X-ray systems only can preset a limited number of positions for automatic positioning, and the preset position should be selected by a radiographer before automatically positioning at the preset position.
For a hospital with heavy load, a radiographer may often deal with various patients. The limited number of preset positions in the existing digital X-ray systems is far from satisfying clinical needs. In addition, during the practical operation, a radiographer often needs to manually adjust the positioner of the X-ray system, in order to better adjust the position of the field of view for exposure. Generally, in some hospitals, it may need to image several hundreds of patients every day, and during the diagnosis, the field of view for exposure of the X-ray system should be manually adjusted almost for each patient, which, for a radiographer, particularly for a female radiographer, is a huge challenge.
In addition, when a radiographer wants to ensure that the region of the field of view is acceptable, he needs to turn on the lamp of the collimator, and at this time, a laser cross cursor for demarcating the position of the detector appears; however, the laser cross cursor is not patient friendly, and sometimes may hurt eyes of the patient.
Currently, each protocol in an X-ray system is provided with a default FOV value (i.e., the size of the FOV region). However, the default value may sometimes not be suitable for a patient whose body size is rather different. At this time, a radiographer is required to manually modify the FOV value, which will increase the time required for the whole examination and the work flow. If the radiographer is unwilling to manually modify the FOV value, some patients may expose to excessive dose of radiation which will be very dangerous.